Engines may use various forms of fuel delivery to provide a desired amount of fuel for combustion in each cylinder. One type of fuel delivery uses a port injector for each cylinder to deliver fuel to respective cylinders. Still another type of fuel delivery uses a direct injector for each cylinder.
Engines have also been described using more than one injector to provide fuel to a single cylinder in an attempt to improve engine performance. Specifically, in US 2005/0155578 an engine is described using a port fuel injector and a direct injector in each cylinder of the engine.
Another approach utilizing multiple injection locations for different fuel types is described in the papers titled “Calculations of Knock Suppression in Highly Turbocharged Gasoline/Ethanol Engines Using Direct Ethanol Injection” and “Direct Injection Ethanol Boosted Gasoline Engine: Biofuel Leveraging for Cost Effective Reduction of Oil Dependence and CO2 Emissions” by Heywood et al. Specifically, the Heywood et al. papers describes directly injecting ethanol to improve charge cooling effects, while relying on port injected gasoline for providing the majority of combusted fuel over a drive cycle.
However, the inventors herein have recognized several ways to operate such systems with improved performance during engine starting. In one example, the inventors have recognized that using fuel injection from a first fuel injector (e.g., a port fuel injector) provides improved starting under colder conditions, whereas using fuel injection from a second fuel injector (e.g., a direct fuel injector) provides improved starting under hot-restart operation. In another example, the inventors herein have further recognized there may be conditions where using both a first and second fuel injector may provide improved starting. In still another example, the inventors herein have recognized that when starting with a first injector, a time when acceptable combustion using the second injector may be possible can be identified based on a number of combustion events.
Thus, in one example, a system for an engine of a vehicle is provided, comprising: a cylinder of the engine; a first injector configured to inject a first fuel to said cylinder; a second injector configured to inject a second fuel to said cylinder; a controller configured to, during a first operating condition, commence combustion in the engine by injecting fuel into said cylinder from only said first injector during a first start, and during a second operating condition, to commence combustion in the engine by injecting fuel into said cylinder from only said second injector during a second start.
In this way, an appropriate injection may be made depending on operating conditions to enable efficient engine starting under varying conditions.
In another example, a system for an engine of a vehicle is provided, comprising: a cylinder of the engine; a first injector configured to inject a first substance to said cylinder; a second injector configured to inject a second substance to said cylinder; a controller configured to perform combustion in the engine by injecting fuel into said cylinder, where said fuel is injected by only one of said first and second injectors during selected engine starting conditions, and injection by the other of said injectors is enabled based on number of events from a start of the engine.
In this way, it is possible to provide consistent injection from a second injector based on the number of combustion events, thereby providing improved starting performance.
In still another example, a system for an engine of a vehicle is provided, comprising: a cylinder of the engine; a first injector configured to inject a first fuel to said cylinder; a second injector configured to inject a second fuel to said cylinder; a controller configured to, during a first operating condition, commence combustion in the engine by injecting fuel into said cylinder from at least said first injector during a first start, and during a second operating condition, to commence combustion in the engine by injecting fuel into said cylinder from at least said second injector during a second start.
Again, in this way, an appropriate injection or injections may be made depending on operating conditions to enable efficient engine starting under varying conditions. For example, under some conditions, injections from the first injector may be used during starting, and under other conditions, injections from both the first and second injector may be used during starting.